Shifting "improved margin bound" -> "improved averaging bound" because
it seems a little more descriptive.

I have resolved several dangling references.

Added 'sqrt' which seems to have been lost from the definition of the
margin bound.

Removed "Recall that until now we have arbitrarily fixed $N$ and
$\theta$."  because the wording was bad and I couldn't think how to
fix it.

Added lots of detail and a graph for the examples.


